Making Sound• a longitudinal wave

• produced when matter vibrates

– this in turn, causes the medium in which it is in to vibrate

• ex: tuning fork (the matter)

vibrates so the air (the medium)

vibrates

Speed of Sound• At room temp., travels 760 mph

• How fast sound travels is determined by Temperature, Elasticity, and Density of the medium it travels through.

– the higher the temperature the faster sound travels because particles can move faster

– the more elastic the material, the faster sound travels

– density varies, but often travels faster in denser materials

– breaking the speed of sound in air creates a sonic boom

Properties of Sound1. Pitch

– depends on the frequency of the wave

• high frequency = high pitch

• low frequency = low pitch

– Humans can hear sound from 20 Hz to 20,000 Hz.

– Ultrasonic waves are above 20,000 Hz

• dog whistle

– Infrasonic waves are below 20 Hz

• moving your hand

Range of frequencies or pitches that humans and various animals can hear

• Doppler Effect

– a change in pitch because there is motion between the sound and the person listening to it• moving towards you = higher pitch because

waves are being compressed• moving away from you = lower pitch because

waves are being spread out

Doppler Effect Animation

Horn Sound

2. Intensity– amount of energy carried by the wave– the greater the compression (amplitude) the

louder the sound– unit of measurement is the decibel (dB)

• every 10 decibels is about twice as loud• over 100 dB could start to damage hearing